1. A Beis Din may always retract its ruling in cases of Dinei Mamonos, but in Dinei Nefashos not every ruling may be retracted.

2. If a Beis Din of non-Mumchim issued an erroneous ruling in Dinei Mamonos or regarding the Dinim of Tum'ah and Taharah, they may not retract it.

3. If a Beis Din errs in a Devar Mishnah, the Din is overturned.

4. If a Beis Din errs in Shikul Ha'Da'as the Din is not overturned.

5. Rav Chisda maintains that if the Beis Din personally carries out its ruling, the Din is not overturned and the judges must pay for their mistakes.

6. Once Beis Din has reached a verdict in a case of Dinei Nefashos, they may retract it for Zechus but not for Chov.

7. Once Beis Din has reached a verdict in a case of a Mesis, they may retract it for Chov but not for Zechus.

8. If Beis Din errs in a Din on which even the Tzedukim agree, they may reopen the case and try the defendant again even if they originally found him to be Patur.

9. There is a Machlokes regarding whether witnesses may voice their opinion while Beis Din is attempting to reach a verdict in a case of Dinei Nefashos.

A BIT MORE

1. In a case of Dinei Mamonos, a Beis Din is permitted to retract its ruling regardless of whether the defendant was found to be innocent or guilty. In a case of Dinei Nefashos, only a guilty verdict may be retracted, but Beis Din may not retract its ruling if the defendant was found to be innocent.

2. If a Beis Din consisting of Mumchim issues an erroneous ruling, they are Patur from paying the damaged party. If a greater Chacham confirms that they erred, they are also permitted to retract their ruling. However, a Beis Din consisting of non-Mumchim may not retract an erroneous ruling because the Ba'al Din can argue that their second position is no more reliable than their original ruling. Furthermore, a Beis Din of non-Mumchim that issues an erroneous ruling must compensate the damaged party.

3. If the Beis Din errs in a Din which is stated explicitly in a Mishnah or Beraisa, or even by Rav, Shmuel, Ravina, or Rav Ashi, the Din is overturned and consequently there is no requirement for the Beis Din to pay for their error. The Beis Din is Patur from paying even if the Din was already carried out and no longer can be overturned. For instance, if the Beis Din erroneously ruled that a certain animal was a Tereifah and the animal was fed to a dog, the Beis Din is Patur from paying because the Din would have been overturned if the animal was still alive.

4. If a Beis Din rules in accordance with one side of a Machlokes in Halachah but most judges follow the other opinion in that Machlokes, the Beis Din is considered to have made an error in Shikul ha'Da'as and the Din is not overturned.

5. If the judges on a Beis Din carry out their ruling with their own hands, they may not retract their ruling afterwards. For example, if a Beis Din rules that a borrower is Chayav to pay the lender and the judges themselves take money from the borrower and give it to the lender, they may not subsequently retract their ruling. Similarly, they may not retract their ruling if they ruled that the borrower is Patur and they took the Mashkon from the lender and returned it to the borrower. In a case of Tum'ah and Taharah, Beis Din is considered to have carried out their own ruling if they ruled that produce was Tamei and they were Metamei it with a Sheretz, or if they ruled that it is Tahor and they mixed it with other produce, thereby causing the other produce to become Tamei.

6. If a defendant was found to be Chayav Misah, Galus, or Malkus and someone finds a reason to acquit him, he is brought back to Beis Din so they can reconsider the case. However, if a defendant was found to be Patur, Beis Din does not reopen the case even if a reason is discovered for Beis Din to find him Chayav.

7. The Torah says that Beis Din may not show mercy to a Mesis. Therefore, once a Beis Din has ruled that a Mesis is Chayav, the case is not reopened even if a reason is discovered to acquit him. However, if a Mesis was found to be Patur and subsequently a reason is discovered to find him Chayav, the case is reopened and he must be brought back to the Beis Din.

8. Beis Din is usually not permitted to reopen a Din Torah once they have ruled that the defendant is Patur from Misah or Malkus. However, if they erred with regard to a Din that is so explicit in the Torah and that even the Tzedukim agree to it, the defendant is brought back to Beis Din and Beis Din may reverse their ruling and declare that he is Chayav.

9. According to the Tana Kama, the witnesses in a court case may not voice their opinions even if they are aware of a reason to convict or acquit the defendant. Rebbi Yosi Bar Yehudah maintains that the witnesses are permitted to make arguments in the Zechus of the defendant. Even the Tana Kama agrees that the Talmidim may present their own arguments for the Zechus of the defendant.